Wednesday, 21 February 2018

Antenna 'Master'!

Whilst looking at images for ADS-B antennas this evening on Google, I spotted my own groundplane design with the hairpin match, but it wasnt a link to this blog! It was this discussion here https://discussions.flightaware.com/t/built-my-first-antenna-and-doubled-my-coverage/15770/241 where my antenna was discussed with the mention that it was built 'by a master'!

Sadly not! However, it has prompted me to look at how to use my spectrum analyser and tracking generator to test these antennas, since my antenna analyser only goes up to 160MHz! Looks like I need to get a directional coupler!



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Tuesday, 20 February 2018

Plans afoot for Mast-head ADS-B system

The Raspberry Pi 2B based ADS-B receiver system has now been operating succesfully for over 24h, feeding data into the 360radar servers, and so I am now an official contributor and have my log-in's for access to the system.

So the next task is to work to rebuild the receiver system into a self contained system that can be mounted in its entirety at the mast-head, in order to gain the clearest view of the sky, for the furthest range, and at the lowest possible signal loss.

There are a number of difficulties with this, but principly they come down to power feed and data feed.  WiFi could be used, and indeed I have ordered a Raspberry Pi ZeroW to play with this option. The Pi zeroW is a smaller board than the Pi 2/2B or 3, but with less physical connectivity, it only has one USB micro port, unlike the 2B with its four standard USB sockets, and it has no Ethernet port. But it does have on-board WiFi and Bluetooth.

The power feed is the other issue. If using WiFi, then just a DC supply is needed. But the cost of suitably rated DC cable is no cheaper than exterior grade CAT5, and Ethernet would be a more reliable data connection than WiFi (and more secure). This brings up the possibility of using PoE (Power over Ethernet) as a convenient means of supplying the system with power.

I did briefly toy with an alternative board, the Orange Pi, as this is smaller than the R-Pi and could apparently do PoE 'natively'. Sounded good, but the chipsets are different which would have meant much difficulty in compiling the code. This idea ive abandoned once I discovered that the 'native' PoE was simply LAN pins 4 and 5 being available at solder pads. No buck converter or low drop-out 5V regulator is provided, meaning that to provide any meaningful PoE capability I would have to add a Buck Converter anyway! So its easier to stay with the R-Pi and use PoE injectors/splitters.

A colleague has sent me another R-Pi, not sure which model as yet, in order that I can release Sams 2B back to him, rather than embed it in the system. Many thanks Mike! Im looking forward to receiving this unit and seeing what modifications are needed, if any, to my plan.

So, on then to the plan! The plan is cunning... and simplistic. The R-Pi, RTL dongle, Buck Converter, and Antenna, will all be enclosed within a suitable weather radome. Lets look at the total system, from air-side to data link side -

The antenna, which is built on the body of a chassis mount BNC socket, is connected via a BNC patch lead to a BNC to MCX pigtail cable. To reduce losses in future I may replace the patch lead with a BNC-BNC adaptor, or change the BNC to MCX pigtail, which is a chassis BNC socket, to one with a BNC male flying plug.

The MCX connector plugs into the RTL SDR dongles antenna socket. The dongle will be removed from its plastic case and mounted bare, with its chip being fitted with a heatsink. So much for the RF side. Now the fun starts...

The RTL dongle is power hungry, ive measured its current draw at 280mA. This is more than really sensible for the R-Pi's USB ports. So, a Y-splitter cable, with two female and one male USB connector, will be used to seperate the R-Pi's USB port and allow a higher current power feed. The RTL dongle will plug into one of the female connectors, and the male connector into the R-Pi. The remaining female connector will have a USB break out module inserted, which allows me to make direct connections. To this will be connected a short microUSB plug cable, Vbus and Gnd only, this is the power feed to the R-Pi. Two more slightly heavier gauge wires will connect Vbus and Gnd of this break-out board to the output of a Buck Converter module. There should be no need to isolate the Buck Converters supply from that of the R-Pi's USB port, but I may do so anyway, this should be just a case of lifting the appropriate polyfuse on the board, or otherwise isolating the boards 5v rail from one of the USB sockets.

So thats the RF and local system power sorted. Now for the data link and PoE.

A low cost PoE splitter will connect the incoming CAT5 cable to the R-Pi's Ethernet port. The 2.1mm DC socket of this splitter will then connect to the input of the Buck Converter. This I 'might' do with a proper 2.1mm DC jack, if I can be bothered, or I may cut the connector off and hard wire it to the module. It probably doesnt matter. Its probably sensible to add a fuse at this point though.

And that, apart from a suitable waterproof cable gland, a sturdy radome and some pole mounting hardware, is the head end system in its entirety!

All that remains then is the 'interface' end - where the system connects to the LAN and hence on to the internet. This is really very simple. The other half of the PoE pair - the Injector - will connect between the CAT5 cable run and the router. A suitably rated DC power supply then feeds into the injector, which feeds this up the unused 4,5/7,8 cores of the CAT5 cable. Here we have to account for the resistive losses of the run length, and the current maximum ratings of the cable, which is 577mA per core.

At the head end, we want to be able to provide a minimum of 10W. As this is a 5V system, that means 2A. Clearly this cant be done within the cable rating even ignoring resistance loss. This of course is why we have the Buck Converter!

As we have two cores to carry supply, we have a maximum current capacity of just over 1.1A. But i'd rather derate the cable to no more than 500mA per core. Using a 12V supply we can have 416mA per core, even better is to go up to 24V or even, if possible 48V, where we would have little over 100mA per core, for a 10W power total. So anywhere between 24-48V will be ideal, depending on what power packs I can get my paws on. Ideally, a mod to the Router will be made to allow the router and PoE all to run on just one efficient PSU.

So all the necessary parts are either in stock or on order, other than a PSU, and a suitable housing. I suspect however that will end up being PVC pipe, as I can get suitable end caps etc, and it will all seal nicely.

In the meantime, while I await delivery of the parts, I have a 1:72 scale Sopwith Camel to build!

Sorry, no pictures with this post! But hey, have £50 on me -

On each blog post  I will be including the following link -
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This is my own personal referral link, not an advert! I am with Bulb for gas and electricity. Do your own research, but if you decide to switch to them, do so via the above link, and we both get a £50 credit!


Sunday, 18 February 2018

ADS-B reception again

Its been some time since I played with receiving ADS-B signals from aircraft, but with the prospect of being able to track military flights in return for contributing data, I looked again at the 360radar website.

In order to contribute, you of course need to be able to receive, decode, and upload the ADS-B 'squitters'. The easiest way to do this for us was to make use of one of the RTL SDR dongles I have, plus Sams Raspberry Pi 2B single board computer


The 360radar website contains all the instructions needed to install the necessary software and get the system working, so between me and Sam we followed this and soon had decoded signals from a slack handful of aircraft using the dongles crappy stock magmount antenna stuck to the top of a Horlicks tin.

The next job then was to improve the antenna. I decided on  a simple 1/4 wave ground-plane design, but utilised twelve radials over the normal four, the resulting ground-plane at the frequency in question, 1.09GHz, being to RF all but solid. This antenna was built around a spare panel mount BNC socket

What was awkward was soldering the elements on! A 45W iron is not quite powerful enough for the job! It worked, but was hard to do. Ive ordered a 150W iron for any future heavy tasks like this!

With the new antenna just held close to vertical temporarily the resulting increase in received aircraft was astounding! from around 5-8 to 50-60!


However, since all this was rigged on Sams windowsill, it couldnt stay this way. So I had to create a stand to mount the antenna on, so that it can remain in use for some time, until we get the system compact and contained for mast-head mounting.


Theres nothing flash about this mount. Its literally a bit of PVC conduit, rammed into a hole in a block of wood, with a BNC to BNC patch lead in it!


And here it is with the antenna mounted and the receiver connected. It keeps it vertical, and more to the point tidy. The screenshot below shows a moment in the decoded aircraft signals using this antenna.


More work is required, for a start I need to let Sam have his R-Pi back!  So the software will need to be installed on another R-Pi that im arranging to obtain, and the whole thing - antenna, receiver and computer, mounted into a weatherproof radome for installing on the roof apex mast. I plan on running another length of external grade CAT5 cable for this, and making use of PoEt (Power over Ethernet), so I also have some PoEt adapters on order.

Ive received the amplifiers that I intend to use with the HB100 radar modules as well, so will need to fit that experiment in soon.


On each blog post  I will be including the following link -
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Friday, 2 February 2018

First Experiments with HB100 Doppler RADAR Modules

 Cor blimey! Aint it cold!!!

These past few days here have been enough to freeze the balls off of a brass monkey! (although monkeys were never made of brass for this exact reason - if you dont know what a 'monkey' is, research naval gunnery in the 18th century!). If your finding that your gas bill is extortionate this time of year, take a look at the link at the bottom of this page!

The HB100 Doppler RADAR module is the modern equivalent of the old X-band Gunn diode modules that many of us used for 10GHz WBFM back in the 80's and 90's. And they cost very little. I have two of these to experiment with.

The ultimate goal of course is to use them for 10GHz WBFM amateur radio, but they are somewhat harder to use in this manner than the old Gunn modules were.

Instead, as a project for my son who is well into his coding, we are looking at a simple RADAR speed gun project. To this end, I had a little play with one yesterday.

Nothing very special, and no pictures im afraid for this post. Simply a test that they do in fact work. I took one of the modules and connected its IF output to the 'scope, and gave it a clean regulated 5V supply. The output is extremely low level, we are talking just a handful of mV here, and is a variable audio frequency, dependent on the speed of the target, which in this case was just my hand being waved about! But - I could detect an output waveform.

Next step is to add a suitable IF amplifier chain to bring the output level up to around 3V or so, suitable for shaping and feeding into an Arduino.

Also yesterday, I finally joined the Milscanners group and programmed by UBC-125XT scanner up with the UKs military airband frequencies that are most likely to be receivable from the shack. Im quite surprised to be able to hear aircraft at low level all the way down to RAF Cranwell, and extremely pleased to be able to hear at good level aircraft at the Donna Nook gunnery range. The trick now will be to identify any frequencies that I just cant get any traffic on and remove them - as there are still around 60 air defence channels I want to add but have run out of memories!



On each blog post  I will be including the following link -
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This is my own personal referral link, not an advert! I am with Bulb for gas and electricity. Do your own research, but if you decide to switch to them, do so via the above link, and we both get a £50 credit!

Sunday, 28 January 2018

Converting the LED Emergency Lights

Well the Buck Converter modules arrives a couple of weeks ago, but its been too cold to be in the workshop for long, so ive only just got around to progressing this,

The original plan was to remove ALL components from the original boards, both through-hole and SMT, except for the Constant Current Driver. This proved to be impossible as the SMT parts are all glued on! So instead, I decided to isolate the driver IC by milling away the track and the SMT parts in the area around it!

This first board you can see the result of attempting to remove the SMT parts with the heat gun!
I also decided to keep one of the fuse holders in place for the 12v feed to the Buck Converter. Using the original track on the board allowed short bridge wires to be used to connect the module, with a bit of hotmelt glue to hold it in place


The 10 turn preset for setting the output voltage seems to have far too many turns than required - it took a fair bit of 'screwing down' to reach the 3.9V required. Next step is to connect this to the Driver IC, add any other required parts (bypass capacitors etc), replace any poor output LEDs, and wire it all up. An on/off switch will be added to the casing.

Although I do have a lot of 5mm white LEDs, Ive also started to salvage the ones in my now failed Black & Decker LED worklight.

As Sam is becoming a very competent programmer, we've also decided on another Arduino project. As I obtained a couple of HB100 10GHz doppler radar modules some time back, we are going to build a speed gun!



On each blog post  I will be including the following link -
 £50 credit if you switch energy supplier to Bulb Ltd
This is my own personal referral link, not an advert! I am with Bulb for gas and electricity. Do your own research, but if you decide to switch to them, do so via the above link, and we both get a £50 credit!

Sunday, 17 December 2017

Homebrewing

of both varieties!

Its been quite a while since I did much radio, so today I finally shifted the heap of spares and other bits off of the shack desk. A quick tune about showed the HF propagation to be next to nowt, so instead contented myself with finally working out the best way to connect my keyer and twin paddle key up!


This involved making up a custom cable, allowing me to connect the phono connector keying output on the keyer, to the screw terminal posts on my Kent straight key. This was a bit confusing at first, as the HF transceiver would go into Tx and stay transmitting! This turned out to be due to having the key line inverted!

A handful of test transmissions later and the keying is up and running. Ive also added four rubber feet to the twin paddle, which helps stop it sliding around the desk!

The other homebrewing ive been doing, was to start a 6 liter batch of Turbo Cider, and a tropical WOW wine. Unfortunately, this cost me more than expected, when I found that the ambient temperatures were too low, and had to invest in a heat tray! But the cider is now bubbling away merrily.

The WOW wine, is somewhat experimental. I have calculated the ingredients (sugar content) of this to drive a sachet of High Alcohol yeast to its limits. This should hit 18% ABV, if not more! It is also based on a tropical juice mix! Ive no ideal how it will turn out, but the must smelt and tasted amazing! I suppose I will know in a few weeks!

Tomorrow is the first performance of my youngest lads school Christmas show. There was something of a panic on Friday that the show would be without stage lighting, when it was discovered the DMX controller wouldnt work! A call went out for anyone with knowledge of stage lighting to contact the school...

...well, its about 20 years since I worked on stage lighting, and ive no experience of DMX, but I offered my services anyway, on the presumption that it would likely be a simple fault.

And indeed it was. The DC input socket had been flexed a bit too much and the PCB track at the positive socket pin has cracked.


Around half an hour in the workshop, and I had linked out all the power input connections to the nearest suitable solid connection. The school had their controller back, fully working, by the end of the school day.

Ive also finally been bothered to reconnect the power supply to my WSPR beacon. This I will leave on 40m for a while.



On each blog post  I will be including the following link -
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This is my own personal referral link, not an advert! I am with Bulb for gas and electricity. Do your own research, but if you decide to switch to them, do so via the above link, and we both get a £50 credit!

Tuesday, 12 December 2017

LED Emergency Lights - Arranging for 12v supply

Apart from the need to test a number of individual LEDs on each of these Emergency Lamps, which are considerably dimmer than the others (so might need replacing from my LED stock), the big problem with repurposing these lamps is the need to arrange for the 3.9v constant currant LED array to be fed from a 12v source. The on-board 7135 current regulator cannot handle above 6v input, so I need an efficient way to drop 12v at about half an amp, down to between 4-6v for the current regulator.

I had planned on using 7805 linear positive 3-terminal devices, but using these to drop 8v at 500mA will consume 4W and they will get damn hot. Plus theres then the hassle of arranging smoothing and decoupling.

So, at the risk of having to wait for them to arrive from China, ive opted to go for pre-built Buck Converter modules based on the LM2596 device.

At under a sov each, I cant build them for this price! And being adjustable, I can set the output of the module to correspond with a sweet spot in the input range of the 7135 device. These devices, being switching converters, are considerably more efficient than the linear 7805, so should run much cooler.

I could probably arrange to trickle charge the 3.9v 1500mA NiCd packs in each lamp as well.


On each blog post  I will be including the following link -
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This is my own personal referral link, not an advert! I am with Bulb for gas and electricity. Do your own research, but if you decide to switch to them, do so via the above link, and we both get a £50 credit!

Brrrr Its bloody cold

Having had a sick little monster to look after today, ive not ventured out of the house, other than to check Milly the rabbits water and go to the recycling bins.

I had planned on going for a woodland walk with the camera, plus a little shopping, this morning, followed by an hour or two out with the detector in the afternoon. Instead, my car has now sat for 26h covered in ice, and will remain sat that way until 07:00 tomorrow - at which time, I will attempt to get it started for the quarter mile drive to the garage, where it is booked in to have the starter motor replaced! The failing starter is most unreliable when cold....

Im also mildy annoyed. I have, or rather had,  a couple of items on order from 7dayshop. I was hoping these would arrive tomorrow as they are part of a christmas gift. I discovered today that, without any word, they had cancelled and refunded my order! Apparently the items were out of stock - not according to the website when ordered!

A word to suppliers -
1) make sure your stock control algorithm works and update your webpages!
2) if you have to cancel someones order, at least put a note on saying why!

As it happens, I found a suitable alternative, despite not being offered one, and ended up re-ordering from 7dayshop, since they are still the cheapest, reliable supplier I know. I did also manage to find a voucher code, so got a couple % off, meaning I only had to spend an extra 70p or so.




On each blog post  I will be including the following link -
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This is my own personal referral link, not an advert! I am with Bulb for gas and electricity. Do your own research, but if you decide to switch to them, do so via the above link, and we both get a £50 credit! 

Monday, 11 December 2017

Free fermentation bucket!

Someone at work brought in the remains of their kids Halloween sweets a while back, which came in a big tub. This was a 5kg Swizzles Party Pack


Once empty, I noticed it had a really good tight fitting lid, and was marked as food safe polypropylene. Hmmm, thinks me - I bet that has around 8 or so litres volume, would make a good fermentation bucket!

So, I 'claimed' it. Filling it one litre at a time with water, and marking it off, it turns out it holds 12L when filled right to the top.

I also noted a small, slightly thicker spot on the lid, perhaps something to do with the molding machine. Using a tapered drill bit, and a spare airlock as a gauge, I drilled a hole here until the airlock 'almost' fit, then proceeded to cut one turn at a time, until the airlock would push in snugly. 


Hey Presto! A 12L fermentation bucket absolutely free! Just in time to put on a gallon of Turbo Cider this week!

On each blog post  I will be including the following link -
 £50 credit if you switch energy supplier to Bulb Ltd
This is my own personal referral link, not an advert! I am with Bulb for gas and electricity. Do your own research, but if you decide to switch to them, do so via the above link, and we both get a £50 credit!

Tuesday, 5 December 2017

LED Escape Lights - Repurposing

My two boys have, for their play 'crib', a large shed. But this time of year they get little use from it, because its dark.

It just so happens though, that Ive acquired a pair of LED Emergency Escape Lights - the sort of thing you see over fire exits. Now, these are supposed to sit there, connected to the mains, keeping an internal battery charged, until such time as the mains fails, and then they illuminate for 30mins, to provide a guide for anyone attempting to escape a dark and possibly smoke filled building.

The pair Ive obtained each have an array of 27 5mm white LEDs, along with the charging and control circuit board and a 3.9v 1500mAh NiCd battery.


 Immediately, the possibility of converting these into 12v 'penthouse' lamps comes to mind. A 12v system is safe enough that I can let the boys have full control over it - so long as the supply is secure. In this case, the supply will be a large Sealed Lead Acid Battery, so all thats needed is a box.

The LEDs are arranged in parallel groups of three, each group with a 1ohm current limit resistor, on a single long PCB strip. The majority of the main PCB in each lamp is the mains switch mode inverter and battery charger circuit.


Most of the mainboards circuitry is therefore of no use for the new application. The only part that is, is the small black device in the center of the photo below



This is a 7135 Low Drop Out constant current regulator. Its job, is to provide a fixed 350mA drive to the LEDs. This works out at around 13mA per LED at 3v.

There is one problem though - the 7135 has a maximum input voltage of 6v! So, a further regulator, or other voltage dropping technique, is still required to bring the 12v supply down to within the 3-6v range of the 7135. Luckily, the industry standard 7805 1A 5v regulator, is incredibly cheap, and I likely have several in stock.



On each blog post  I will be including the following link -
 £50 credit if you switch energy supplier to Bulb Ltd
This is my own personal referral link, not an advert! I am with Bulb for gas and electricity. Do your own research, but if you decide to switch to them, do so via the above link, and we both get a £50 credit!